Metal Finishing Guide Book

2011-2012 Surface Finishing Guidebook

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Table XXII. Zinc Alloy Compositions Alloy Pure % Zinc 99.9+ Zamak 3 Zamak 5 Zamak 2 Slush Slush Drawn Balance Balance Balance Balance Balance Balance % Aluminum % Magnesium % Copper — — 4.0 4.0 4.0 4.75 5.5 — 0.04 0.04 0.03 — — — — — 1.0 3.0 0.25 — — % Lead — — — — — — 0.08 1. Mild to moderately alkaline soak cleaner. 2. 5% v/v sulfuric acid dip. Neutralizes and conditions the surface. 3. Chemically polish in either a peroxide-type or sulfuric acid/iron salts blend. Both solutions are wetted and specially inhibited. 4. Tarnish inhibit in dip application using either a soap (mechanical tarnish inhibit film) or a benzotriazole (active surface antioxidant). 5. Optionally lacquer (dip or electrolytic) or apply electrolytic chromate. Inconel This alloy constituent typically contains 13.5% nickel and 6.0% chromium. (Note: one alloy type may contain 2% silicon.) Surface preparation cycle: 1. Alkaline soak clean. Mild to moderate alkalinity with sufficient detergency. 2. Acid dip. 20-30% v/v hydrochloric acid for primary oxide removal. 3. Anodically etch. Wood's nickel strike, 100-120°F (38-49°C), 50 A/ft2 20-30 sec. 4. Strike plate cathodic. Woods' nickel strike, 100-120°F (38-49°C), 50 A/ft2 , 2-3 min. 5. Rinse well, proceed to plating bath. The above cycle is sufficient for Inconel X and Hastelloy C. Nickel and Nickel Alloys Require similar treatment as stainless steels. Anodically etch at 15 to 25 A/ft2 in the Woods' strike, or at 40 to 60 A/ft2 for 1 to 3 minutes in a 25% v/v sulfuric acid solution. Next, cathodically condition at 150 to 225 A/ft2 F (24-32° el plated parts and rejects. Powdered Metal Same recommended surface preparation steps as for cast iron. Rinsing is very important, to facilitate drainage and removal of previous contaminating solutions. Silver 132 in a sulfuric acid/flu- oride/chloride solution. Parts not long aged may also be activated in an immer- sion dip consisting of 5 tp 10% v/v sulfuric acid and 2 to 4 oz/gal of potassium iodide at 75 to 90° C). These treatments also apply for replating aged nick- ,

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